Method of manufacturing composite wire products having a tungsten core and a magnetic covering

ABSTRACT

A tungsten wire core is covered with a sheath of silicon carbide, over which a conductive metal coating is applied such as aluminum, nickel or the like which wets, but does not chemically react with the silicon carbide; a magnetic nickel-iron compound is then applied over the metal coating, the metal coating providing a good conductive surface beneath the magnetic cover. The resultant composite wire core has an average tensile strength of 220 kg/mm2 and a modulus of elasticity of 40,000 kg/mm2.

United States Patent Marchal et a1. June 6, 1972 [54] METHOD OFMANUFACTURING 3,124,490 3/ 1964 Schmeckenbecher ..1 17/238 X COMPOSITEWIRE PRODUCTS 3332 33 31323 2225215213 "1137227; HAVING A TUNGSTEN COREAND A 3:327:297 6/1967 c1011 ....117 23s x MAGNETIC COVERING 3,370,9292/ 1968 Mathias .340/174 PW 3,410,715 11/1968 l-lough ...ll7/23l X [72]Inventors. Ilglichel MazchalizPalalszaut; J3? Bouygues, 3,416,95112/1968 floughmu W] 7/106 C 0565* 3,525,638 8/1970 Archey ..117/240 I 73I Assignuez Cnmpagnie Francaise Thomson Houston- Holchkiss Brandt Paris,France Primary ExaminerAlfred L. Leavitt [22 1 Fiied; Man 25 19 9Assistant Examiner-Cameron K. Weiffenbach AtmrneyFlynn & Frishauf 1 [2]]Appl. No.: 811,281

[57] ABSTRACT [52] U.S. Cl. ..29/195, 1 17/l06 C, 1 17/107, A tungstcnwire core is covcred with a sheath of ilicon carl17/l07.2 R, 1 17/114 R,117/114 C, 117/217, bide, over which a conductive metal coating isapplied such as 1 17/231, 1 17/238, 1 17/239, 1 17/240 aluminum, nickelor the like which wets, but does not chemi- [51] lnt.Cl ..Gl 1b 5/66,B44d l/16,B44d 1/06, cally react with the silicon carbide; a magneticnickel-iron C230 1l/08, C23c 11/02 compound is then applied over themetal coating, the metal [58] Field of Search ..1 17/1 14 R, l 14 C, 106C, 107, coating providing a good conductive surface beneath the mag- 17/107.2, 238, 239, 240, 217, 231; 29/195; nctic cover. The resultantcomposite wire core has an average 340 174 VC 174 pw 174 TF 174 Btensile strength of 220 kg/mm and a modulus of elasticity of 40,000kg/mm [56] References Cited 10 Claims, 1 Drawing Figure UNITED STATESPATENTS 3,054,694 9/1962 Aves, Jr. ..29/195 X 1 H2 3 H2+CH3 Sidg Fe1cos+11'1(co)4 He 9 COVER two-1,2511% WlTH SlLlCON CARBIDE COATING FROM1150-1300c MELT 0F AL.

METHOD OF MANUFACTURING COMPOSITE WIRE PRODUCTS HAVING A TUNGSTEN COREAND A MAGNETIC COVERING The present invention relates to a method ofmanufacturing composite wire products, and to apparatus to carry out themethod, and more particularly to make wires which are covered with amagnetic material and which are strong and rigid. Such wires are usefulin magnetic memory units.

Wires which are used as magnetic memories usually have a non-magneticmetallic core, on which an iron-nickel compound, or alloy is depositedas a cover. The non-magnetic core provides the necessary strength, andform stability and is given the necessary mechanical characteristicssuch as resistance against mechanical deformation, the requiredelasticity or brittleness, as desired, and such *other mechanicalproperties as are necessary for the particular use of the magnetic wire.Specifically, the mechanical properties must be such that the magneticproperties of the material can be essentially uniform, avoiding alllocal variations from a norm. The wires must be capable of being spooledon a reel and then be incorporated in a network of magnetic memory unitswhich are perfectly straight.

Iron-nickel compounds, or alloys are deposited on core units as verythin layers. The magnetic axes of the elementary crystal elements of themagnetic deposits can be aligned to be either parallel to the wire orperpendicular thereto, with as little random orientation as possible.The degree of crystalline perfection, and the absence of internalstresses within the magnetic coating itself greatly affects the qualityof the final magnetic wire obtained. It is desirable that the totaldiameter of the composite wire shall be as small as possible, so that aslittle space as possible is taken up by the apparatus using the memory.

It has previously been proposed to provide wires in which a tungstencore is used on which silicon carbide is vapor deposited utilizing asilane as starting material, arriving at a wire of from 30 to 150microns diameter. Such wires are very rigid and can well be used forregular magnetic networks formed in a crossed array of aligned wires,located side by side, along two axes.

It is an object of the present invention to provide an improved processof making such wires, and apparatus to carry out said process.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, the process uses thesteps of providing a sheath of silicon carbide over a tungsten core, andthen applying a layer of a conductive metal such as aluminum, copper, orthe like which wets, but does not chemically react with the siliconcarbide, over the sheath of silicon carbide; this conductive metal willform a good electrical conductor. Thereafter, from a gaseous mixture ofstarting materials, a magnetic compound of iron and nickel is vapordeposited over the conductive metal.

The apparatus to carry out the method includes a plurality of isolatedreaction chambers, the first being arranged to pass the tungsten wire athigh temperatures so as to anneal the wire, a second to deposit asilicon compound to provide a silicon carbide sheath, and a third toapply magnetic material from a gaseous phase; between the second andthird chambers, the electrically conductive metal is applied over thesilicon carbide sheath, for example by passing the wire through a meltof aluminum, copper, silver, nickel or the like, or by depositing on thewire, from a gaseous phase in an additional reaction chamber, anotherlayer of tungsten, tantalum, niobium, molybdenum, or the like.

The invention will be described by way of example with reference to theaccompanying drawing, wherein the single FIGURE illustrates in schematicform the steps in the process and the apparatus of the presentinvention.

A tungsten wire 1, having a diameter in the order of microns is suppliedfrom pay-out reel 2. It passes, sequentially, through a number ofchambers 3, 4, l5. Successive chambers are sealed from the outside airby mercury traps 5, 6, 7, l6, 17, to isolate the chambers from ambientair and from each other. Electrical conductors 8, 9, 10, 18, 19 areconnected to respective mercury traps, as seen in the figure, to applyelectrical current to wire 1 to heat wire 1 to temperatures necessary tocarry out the process. These mercury traps thus provide the dualfunction of sealing the chambers and additionally providing electricalcontacts so that the wire will reach, within the chambers, certaintemperatures.

Chamber 3 is supplied with hydrogen, carefully purified, to anneal thewire. The wire itself is heated to a temperature between l,l00 and 1,250C. The annealed wire leaving chamber 3 through mercury trap 6 is thenpassed into the second chamber 4, into which a mixture ofmethyltrichlorosilane and hydrogen is applied. By passing currentthrough the wire, supplied over conductors 9, 10, the wire is heated toa temperature between l,l50 and 1,300 C. As the wire passes throughchamber 4, it is covered progressively with a dense and homogeneouslayer of silicon carbide. The speed at which the wire passes through thechambers may be in the order of from 15 to 20 meters per hour.

The thickness of the silicon carbide layer, schematically illustrated at1 l in the figure, and afiecting the diameter of the entire wire, can becontrolled by controlling the richness of the gaseous mixture of themethyltrichlorosilane (H CH Si C1 which is supplied to chamber 4. Thewire can have an average tensile strength of 220 kg/mm and a modulus ofelasticity of 40,000 kg/mm. While the wire is mechanically strong, it isa poor conductor. in order to render it electrically conductive, thesilicon carbide covered tungsten wire is conducted through a moltenmetal bath 12. The melt in bath 12 may, for example, be aluminum inmolten state within a graphite crucible 13. The tungsten wire, sheathedby the silicon carbide, will thus be covered by a thin layer of metal offrom 1 to 5 microns width. The metal will readily wet the siliconcarbide to form a good mechanical bond thereto, without forming achemical composite structure which might detract from the mechanicalproperties of the wire. The thickness of the metal layer may becontrolled by the length of time that the wire is in the melt 12.

Next, the thus covered tungsten wire is passed through a mercury lock 16into a third chamber 15 which may be identical to the chambers 3 and 4.Again, electrical current is applied to conductors 18, 19 to heat thewire to a temperature of from between to 230 C. A gaseous mixture ofnickel carbonyl [Ni (CO),] and iron carbonyl [Fe (CO) is applied to thechamber; the respective proportions are controlled so that a finalmagnetic compound is obtained which will have, for example, 70 percentiron and 30 percent nickel. The carbonyl compounds are mixed in acarrier gas of helium. The gaseous mixture, including the carbonylcompounds, is deposited on the hot wire, liberating iron, nickel andcarbon dioxide. A magnet can be applied to chamber 15, as schematicallyindicated at 25, in order to orient the dipoles of the iron-nickelcompounds to be perpendicular, or parallel to the axis of wire 1.

After leaving the last mercury seal 17, the finished wire 20 is spooledon a take-up reel 21.

The process of the present invention, and the apparatus therefor, may bemodified in various ways; for example, the conductive metal applied inmelt 12 may be copper, silver, or nickel rather than aluminum;alternatively, rather than utiliz ing a melt, a nickel, silver, orcopper plating solution may be placed in tank 13 to apply the metal tothe silicon carbide coated wire. Also, other metals may be used such asmolybdenum, tungsten, tantalum, niobium, or the like, obtained byreaction from a gaseous phase in another reaction chamber similar tochambers 3, 4, 15 and utilized instead of the crucible 13 or a metalplating bath.

The rigid and mechanically strong and stable tungsten core, with thesilicon carbide cover, enables the manufacture of memory units in whichthe space between wires can be carefully controlled. Silicon carbide ischemically practically inert,

I core, a layer of electrically highly conductive non-magnetic metalhaving a thickness of about 1 to microns on said sheath of siliconcarbide, said metal being selected from the group consisting ofaluminum, copper, silver, nickel, tungsten, tantalum, niobium, andmolybdenum;

and, an outer covering of magnetic iron-nickel on said sheathed, metalcovered wire.

2; The composite wire of claim 1 wherein said non-magnetic conductivemetal is aluminum.

3. The composite wire of claim 2 wherein said iron-nickel outer coveringis an iron-nickel compound having crystalline orientation perpendicularor parallel to the axis of said composite wire.

4. The composite wire of claim 1 wherein said non-magnetic conductivemetal is selected from the group consisting of tungsten, niobium,tantalum, and molybdenum.

5. The composite wire of claim 4 wherein said iron-nickel outer coveringis an iron-nickel compound having crystalline orientation perpendicularor parallel to the axis of said composite wire.

6. Method of manufacturing composite wire products having a magneticcovering and a tungsten core comprising covering the core of tungstenwith a sheath of silicon carbide;

applying a layer of a non-magnetic conductive metal which vwets thesilicon carbide but does not chemically react with the silicon carbide,over said sheath of silicon carbide to provide a good electricallyconductive layer by depositing from a gaseousphase ina reaction chamber,at least one metal from the group consisting of tungsten,

. tantalum,'niobium,a'nd molybdenum;

and vapor depositing, from a gaseous mixture as starting material, amagnetic metallic layer on said conductive layer.

7. Method of manufacturing composite wire products hav-' ing a magneticcovering and a tungsten core comprising covering the core of tungstenwith a sheath of silicon carbide; applying a layer of a non-magneticconductive metal which wets the silicon carbide but does not chemicallyreact with the silicon carbide, over said sheath of silicon carbide toprovide a good electrically conductive layer by passing said siliconcarbide sheated wire through a melt of said conductive metal; and vapordepositing, from a gaseous mixture as starting material, a magneticmetallic layer on said conductive layer. i 8. Method according to claim7, wherein said conductive metal is aluminum. 1 9. Method according toclaim 8, wherein said gaseous mixture as starting material for themagnetic compounds comprises carbonyls of iron and carbonyls of nickel,and the magnetic compound is an iron-nickel compound.

10. Method according to claim 9, including the step of magneticallyorienting the iron-nickel compound during deposition thereof.

CERTIFICATE OF COR Patent No.

June 6, 1972 Dated Inventor(s) Michel 8t It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

On the first page of the patent, left column, between lines marked [21]and [52] insert:

April 30, 1968 France. .PV 150017-- Foreign Applieation Priority DataSigned and sealed this 17th day of October 1972 (SEAL) Attest:

EDWARD M; FLETCHER TR Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

2. The composite wire of claim 1 wherein said non-magnetic conductivemetal is aluminum.
 3. The composite wire of claim 2 wherein saidiron-nickel outer covering is an iron-nickel compound having crystallineorientation perpendicular or parallel to the axis of said compositewire.
 4. The composite wire of claim 1 wherein said non-magneticconductive metal is selected from the group consisting of tungsten,niobium, tantalum, and molybdenum.
 5. The composite wire of claim 4wherein said iron-nickel outer covering is an iron-nickel compoundhaving crystalline orientation perpendicular or parallel to the axis ofsaid composite wire.
 6. Method of manufacturing composite wire productshaving a magnetic covering and a tungsten core comprising covering thecore of tungsten with a sheath of silicon carbide; applying a layer of anon-magnetic conductive metal which wets the silicon carbide but doesnot chemically react with the silicon carbide, over said sheath ofsilicon carbide to provide a good electrically conductive layer bydepositing from a gaSeous phase in a reaction chamber, at least onemetal from the group consisting of tungsten, tantalum, niobium, andmolybdenum; and vapor depositing, from a gaseous mixture as startingmaterial, a magnetic metallic layer on said conductive layer.
 7. Methodof manufacturing composite wire products having a magnetic covering anda tungsten core comprising covering the core of tungsten with a sheathof silicon carbide; applying a layer of a non-magnetic conductive metalwhich wets the silicon carbide but does not chemically react with thesilicon carbide, over said sheath of silicon carbide to provide a goodelectrically conductive layer by passing said silicon carbide sheatedwire through a melt of said conductive metal; and vapor depositing, froma gaseous mixture as starting material, a magnetic metallic layer onsaid conductive layer.
 8. Method according to claim 7, wherein saidconductive metal is aluminum.
 9. Method according to claim 8, whereinsaid gaseous mixture as starting material for the magnetic compoundscomprises carbonyls of iron and carbonyls of nickel, and the magneticcompound is an iron-nickel compound.
 10. Method according to claim 9,including the step of magnetically orienting the iron-nickel compoundduring deposition thereof.